Some unit test fixes

tests/lib/unittest/instance_test.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+
+#library('instance_test');
+#import('../../../lib/unittest/unittest.dart');
+#source('test_utils.dart');
+
+doesThrow() { throw 'X'; }
+
+main() {
+  initUtils();
+
+  group('Type Matchers', () {
+    test('isInstanceOf', () {
+      shouldFail(0, new isInstanceOf<String>('String'),
+        "Expected: an instance of String but: was <0>");
+      shouldPass('cow', new isInstanceOf<String>('String'));
+    });
+
+    test('throwsA', () {
+      shouldPass(doesThrow, throwsA(equals('X')));
+      shouldFail(doesThrow, throwsA(equals('Y')),
+        "Expected: throws an exception which matches 'Y' "
+        "but:  no exception or exception does not match 'Y'");
+    });
+  });
+}
+